This invention relates to a rotary actuator. More particularly, this invention relates to a rotary actuator for generating pure torque for moving e.g. a memory data device member such as a data transducer assembly relative to another member such as a concentric track of a rotating data storage disk.
There are two generally known prior art approaches for moving e.g. a data transducer relative to a rotating storage surface such as a storage disk. One prior art approach was to use a linear moving coil electromagnetic actuator, such as illustrated in U.S. Pat. No. 3,737,883 and used in the Hewlett-Packard Model 79Z0A disk drive product, as described in the Hewlett-Packard Journal Aug. 1977, pp. 2-15. The other prior art approach is to use a linear band drive actuator driven by a stepping motor as in the Shugart Associates Model SA1000 disk drive product, as described in a Shugart Associates two page product bulletin dated Sept. 1979 and entitled "8-Inch Fixed Disk Drive", and as further described in co-inventor Joel N. Harrison's prior U.S. Pat. No. 4,418,370.
Rotary actuators have been known and used in various instruments. One such actuator, using a printed circuit rotor segment, is depicted in FIG. 4 of an article entitled "Servo-Controlled Beam Director Provides Major Benefits" published in the Hewlett-Packard Journal, Feb. 1980, pages 24-28. While the printed circuit motor illustrated therein operates to rotate a mirror, it does not apply pure (balanced) torque to the mirror shaft.